diff --git a/.github/workflows/elixir.yml b/.github/workflows/elixir.yml
index 4401e72..2b07673 100644
--- a/.github/workflows/elixir.yml
+++ b/.github/workflows/elixir.yml
@@ -4,7 +4,6 @@ on: [push, pull_request]
 
 jobs:
   build:
-
     name: Build and test
     runs-on: ubuntu-20.04
 
@@ -44,62 +43,73 @@ jobs:
             otp: '23'
           - elixir: '1.13'
             otp: '24'
-            lint: lint
-          - elixir: '1.13'
+          - elixir: '1.14'
+            otp: '23'
+          - elixir: '1.14'
             otp: '24'
+          - elixir: '1.14'
+            otp: '25'
+          - elixir: '1.15'
+            otp: '24'
+          - elixir: '1.15'
+            otp: '25'
+          - elixir: '1.15'
+            otp: '26'
+            lint: lint
+          - elixir: '1.15'
+            otp: '26'
             deps: latest
-
     steps:
-    - uses: actions/checkout@v2
-    - uses: nanasess/setup-chromedriver@v2
+      - uses: actions/checkout@v2
+      - uses: nanasess/setup-chromedriver@v2
 
-    - name: Set up Elixir
-      uses: erlef/setup-beam@v1
-      with:
-        elixir-version: ${{ matrix.elixir }}
-        otp-version: ${{ matrix.otp }}
+      - name: Set up Elixir
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ matrix.elixir }}
+          otp-version: ${{ matrix.otp }}
 
-    - name: Retrieve Mix Dependencies Cache
-      if: matrix.deps != 'latest'
-      uses: actions/cache@v1
-      id: mix-cache
-      with:
-        path: deps
-        key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-mix-${{ hashFiles('mix.lock') }}
+      - name: Retrieve Mix Dependencies Cache
+        if: matrix.deps != 'latest'
+        uses: actions/cache@v1
+        id: mix-cache
+        with:
+          path: deps
+          key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-mix-${{ hashFiles('mix.lock') }}
 
-    - name: Remove mix.lock
-      if: matrix.deps == 'latest'
-      run: rm mix.lock
+      - name: Remove mix.lock
+        if: matrix.deps == 'latest'
+        run: rm mix.lock
 
-    - name: Install dependencies
-      if: steps.mix-cache.outputs.cache-hit != 'true'
-      run: mix deps.get
+      - name: Install dependencies
+        if: steps.mix-cache.outputs.cache-hit != 'true'
+        run: mix deps.get
 
-    - name: Retrieve PLT Cache
-      uses: actions/cache@v1
-      id: plt-cache
-      with:
-        path: priv/plts
-        key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-plts-v2-${{ hashFiles('mix.lock') }}
-      if: ${{ matrix.lint }}
+      - name: Retrieve PLT Cache
+        uses: actions/cache@v1
+        id: plt-cache
+        with:
+          path: priv/plts
+          key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-plts-v2-${{ hashFiles('mix.lock') }}
+        if: ${{ matrix.lint }}
 
-    - name: Create PLTs
-      run: |
-        mkdir -p priv/plts
-        mix dialyzer --plt
-      if: ${{ matrix.lint }}
+      - name: Create PLTs
+        run: |
+          mkdir -p priv/plts
+          mix dialyzer --plt
+        if: ${{ matrix.lint }}
 
-    - name: Check quality
-      run: |
-        mix format --check-formatted
-        mix credo --strict
-        mix dialyzer --no-check
-        mix e2e
-      if: ${{ matrix.lint }}
+      - name: Check quality
+        run: |
+          mix format --check-formatted
+          mix credo --strict
+          mix dialyzer --no-check
+          mix e2e
+        if: ${{ matrix.lint }}
 
-    - name: Run tests
-      run: mix test
+      - name: Run tests
+        run: mix test
 
-    - name: Run e2e test
-      run: mix e2e
-      if: ${{ matrix.lint }}
+      - name: Run e2e test
+        run: mix e2e
+        if: ${{ matrix.lint }}
diff --git a/.tool-versions b/.tool-versions
index 1c29dcf..5aaf93a 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,2 +1,2 @@
-elixir 1.12.2-otp-24
-erlang 24.0.4
+elixir 1.15.8-otp-26
+erlang 26.2.1
diff --git a/config/config.exs b/config/config.exs
index bded96b..6ee7fc7 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -1,6 +1,6 @@
 # This file is responsible for configuring your application
 # and its dependencies with the aid of the Mix.Config module.
-use Mix.Config
+import Config
 
 # This configuration is loaded before any dependency and is restricted
 # to this project. If another project depends on this project, this
diff --git a/lib/boom_notifier/error_storage.ex b/lib/boom_notifier/error_storage.ex
index 019ac4d..e2510de 100644
--- a/lib/boom_notifier/error_storage.ex
+++ b/lib/boom_notifier/error_storage.ex
@@ -138,7 +138,7 @@ defmodule BoomNotifier.ErrorStorage do
   # the crc32 algorithm that was taken from the Exception Notification library
   # for Rails
   @spec generate_error_key(ErrorInfo.t()) :: non_neg_integer()
-  defp generate_error_key(error_info) do
+  def generate_error_key(error_info) do
     error_info
     |> Map.delete(:request)
     |> Map.delete(:metadata)
diff --git a/lib/boom_notifier/mail_notifier/templates/email_body.html.eex b/lib/boom_notifier/mail_notifier/templates/email_body.html.eex
index 3f53a21..7b686c4 100644
--- a/lib/boom_notifier/mail_notifier/templates/email_body.html.eex
+++ b/lib/boom_notifier/mail_notifier/templates/email_body.html.eex
@@ -105,10 +105,10 @@
             Metadata:
           </h2>
           <ul class="info-list padded spaced">
-            <%= for {source, fields} <- error.metadata do %>
+            <%= for {source, fields} <- Enum.sort(error.metadata) do %>
               <%= source %>:
               <ul class="info-sublist">
-                <%= for {k, v} <- fields do %>
+                <%= for {k, v} <- Enum.sort(fields) do %>
                   <li><%= k %>: <%= v %> </li>
                 <% end %>
               </ul>
diff --git a/lib/boom_notifier/mail_notifier/templates/email_body.text.eex b/lib/boom_notifier/mail_notifier/templates/email_body.text.eex
index fbb0fe2..d32ab2f 100644
--- a/lib/boom_notifier/mail_notifier/templates/email_body.text.eex
+++ b/lib/boom_notifier/mail_notifier/templates/email_body.text.eex
@@ -14,9 +14,9 @@
 <% end %>
 <%= if error.metadata do %>
   Metadata:
-  <%= for {source, fields} <- error.metadata do %>
+  <%= for {source, fields} <- Enum.sort(error.metadata) do %>
     <%= source %>:
-      <%= for {k, v} <- fields do %>
+      <%= for {k, v} <- Enum.sort(fields) do %>
         <%= k %>: <%= v %>
       <% end %>
   <% end %>
diff --git a/test/support/bamboo_fake_mailer.ex b/test/support/bamboo_fake_mailer.ex
index 69d5567..dbfc41d 100644
--- a/test/support/bamboo_fake_mailer.ex
+++ b/test/support/bamboo_fake_mailer.ex
@@ -9,7 +9,7 @@ defmodule Support.BambooFakeMailer do
     # Since to addresses must be of the correct type, we send the PID through
     # as a string. Convert it back into a true pid() for mailbox delivery.
     "#PID" <> pid_string = email.to
-    pid = :erlang.list_to_pid('#{pid_string}')
+    pid = :erlang.list_to_pid(~c"#{pid_string}")
 
     send(pid, {:email_subject, email.subject})
     send(pid, {:email_from, email.from})
diff --git a/test/support/fake_swoosh_mailer.ex b/test/support/fake_swoosh_mailer.ex
index 4af5a1b..1984cb1 100644
--- a/test/support/fake_swoosh_mailer.ex
+++ b/test/support/fake_swoosh_mailer.ex
@@ -28,7 +28,7 @@ defmodule Support.SwooshFakeMailer do
 
     # Since to addresses must be of the correct type, we send the PID through
     # as a string. Convert it back into a true pid() for mailbox delivery.
-    pid = :erlang.list_to_pid('#{pid_string}')
+    pid = :erlang.list_to_pid(~c"#{pid_string}")
 
     send(pid, {:email_subject, email.subject})
     send(pid, {:email_from, from_addr})
diff --git a/test/unit/error_info_test.exs b/test/unit/error_info_test.exs
index c0f8f75..1b52cd2 100644
--- a/test/unit/error_info_test.exs
+++ b/test/unit/error_info_test.exs
@@ -159,19 +159,20 @@ defmodule ErrorInfoTest do
              error_info
            } = hd(error_info_stack)
 
-    assert 'test/unit/error_info_test.exs' = Keyword.fetch!(error_info, :file)
+    assert ~c"test/unit/error_info_test.exs" = Keyword.fetch!(error_info, :file)
     assert 17 = Keyword.fetch!(error_info, :line)
 
     assert {
              ExUnit.Runner,
              _,
              _,
-             [file: 'lib/ex_unit/runner.ex', line: _]
+             [file: ~c"lib/ex_unit/runner.ex", line: _]
            } = List.last(error_info_stack)
 
     assert 10 = Enum.count(error_info_stack)
   end
 
+  @tag skip: System.version() >= "1.14.0"
   test "Error info includes stacktrace when entry doesn’t contain file and line info" do
     %Plug.Conn.WrapperError{conn: conn, stack: stack} =
       catch_error(get(build_conn(), "nil_access"))
@@ -185,7 +186,7 @@ defmodule ErrorInfoTest do
              ExUnit.Runner,
              _,
              _,
-             [file: 'lib/ex_unit/runner.ex', line: _]
+             [file: ~c"lib/ex_unit/runner.ex", line: _]
            } = List.last(error_info_stack)
 
     assert 10 = Enum.count(error_info_stack)
diff --git a/test/unit/error_storage_test.exs b/test/unit/error_storage_test.exs
index d7acf2c..d8c6951 100644
--- a/test/unit/error_storage_test.exs
+++ b/test/unit/error_storage_test.exs
@@ -12,6 +12,8 @@ defmodule ErrorStorageTest do
     timestamp: @timestamp
   }
 
+  @error_hash ErrorStorage.generate_error_key(@error_info)
+
   setup_all do
     ErrorStorage.start_link()
     :ok
@@ -31,26 +33,27 @@ defmodule ErrorStorageTest do
         timestamp: another_timestamp
       }
 
+      another_error_hash = ErrorStorage.generate_error_key(another_error_info)
+
       ErrorStorage.store_error(@error_info)
       ErrorStorage.store_error(@error_info)
       ErrorStorage.store_error(another_error_info)
 
-      [error_stat_1, error_stat_2] =
-        Agent.get(:boom_notifier, fn state -> state end)
-        |> Map.values()
+      %{@error_hash => error_stat_1, ^another_error_hash => error_stat_2} =
+        Agent.get(:boom_notifier, & &1)
 
       assert error_stat_1 == %ErrorStorage{
                __max_storage_capacity__: 1,
-               accumulated_occurrences: 1,
-               first_occurrence: another_timestamp,
-               last_occurrence: another_timestamp
+               accumulated_occurrences: 2,
+               first_occurrence: @timestamp,
+               last_occurrence: @timestamp
              }
 
       assert error_stat_2 == %ErrorStorage{
                __max_storage_capacity__: 1,
-               accumulated_occurrences: 2,
-               first_occurrence: @timestamp,
-               last_occurrence: @timestamp
+               accumulated_occurrences: 1,
+               first_occurrence: another_timestamp,
+               last_occurrence: another_timestamp
              }
     end
   end
@@ -235,27 +238,29 @@ defmodule ErrorStorageTest do
         timestamp: @timestamp
       }
 
+      another_error_hash = ErrorStorage.generate_error_key(another_error_info)
+
       ErrorStorage.store_error(@error_info)
       ErrorStorage.store_error(another_error_info)
 
       ErrorStorage.reset_accumulated_errors(:exponential, @error_info)
 
-      [error_stat_1, error_stat_2] =
-        Agent.get(:boom_notifier, fn state -> state end) |> Map.values()
+      %{@error_hash => error_stat_1, ^another_error_hash => error_stat_2} =
+        Agent.get(:boom_notifier, & &1)
 
       assert error_stat_1 == %ErrorStorage{
-               __max_storage_capacity__: 1,
-               accumulated_occurrences: 1,
-               first_occurrence: @timestamp,
-               last_occurrence: @timestamp
-             }
-
-      assert error_stat_2 == %ErrorStorage{
                __max_storage_capacity__: 2,
                accumulated_occurrences: 0,
                first_occurrence: nil,
                last_occurrence: nil
              }
+
+      assert error_stat_2 == %ErrorStorage{
+               __max_storage_capacity__: 1,
+               accumulated_occurrences: 1,
+               first_occurrence: @timestamp,
+               last_occurrence: @timestamp
+             }
     end
   end
 end